How long will the rash last? The duration of the rash depends on whether you've had a rash before. If you've never received a rash from poison oak, ivy or sumac, the rash could last 21 days or longer.

Characteristic cutaneous findings of anti-TIF1-γ positive dermatomyositis, including facial rash, V-neck and back rash, periungual telangiectasias, heliotrope rash, Gottron's sign, palatal patch, and ...